Canadian scientists figure out how to preserve vaccines without refrigeration — a potential public-health game changer

Ali Ashkar (pictured) and other team members have applied to the Gates Foundation for funding, and hope to be in touch with medical and other partners within a year.

Vincent Leung (left), Ali Ashkar (centre) and Fatemeh Vahedi seen at work on the project.

A team of Canadian scientists has developed what could be a simple and inexpensive method to preserve vaccines without refrigeration — a potential public-health game changer in parts of the world where epidemics are raging and resources are limited.

A chemical engineering team at McMaster University, spearheaded by recent PhD graduate Vince Leung and supervised by professor Carlos Filipe, combined herpes and influenza A vaccines — chosen because they’re among the most fragile and sensitive to heat — with a sugar solution and dried the mixture into a thin film.

They stored this at a desert-like 40 degrees Celsius for weeks before reconstituting it in saline solution and testing it in mice.

The vaccines were as safe and as effective as they would have been “fresh out of the fridge,” Filipe said. The flu vaccine was still good after three months, and the herpes after two.

The research, published Tuesday in the journal Scientific Reports , is the first to use this method to preserve vaccines. The team also tested a pneumonia vaccine and an experimental Ebola vaccine using the same process. They passed the test too.

Filipe didn’t see any reason why the process wouldn’t work with a variety of viral vaccines.

“I’m very confident. That’s unusual for me,” he said.

He explained the seeds of the project were planted a few years ago, when one of the paper’s authors, Sana Jahanshahi-Anbuhi — then a grad student, now an assistant professor at Concordia University — had a light-bulb moment in the grocery store.

She looked at the dissolvable Listerine breath strips and had a flash of insight: The strips are thin sheets of film made of a sugar called pullulan. Scientists already knew sugars can help protect the integrity of some fragile biological molecules, such as enzymes. What if they swapped the Listerine ingredients for something else — like a protein or virus from a vaccine? Could sugars protect those too?

They could, as it turned out. Pullulan helps form a barrier around the vaccine molecules that keeps oxygen out, Filipe explained, and it also holds them in place, keeping them from unfolding and breaking up when exposed to heat. A second sugar, trehalose, helped protect the vaccine particles from drying out too much as the mixture was dried into a film.

The next steps will be to put more vaccines to the test, and investigate the safety and efficacy in humans, not just mice. The team has just applied to the Gates Foundation for funding, and Filipe said the team hopes to be in touch with medical and other partners within a year to talk about how to bring the product to market.

One of his big concerns is inertia — a lot of money, time and logistics have been invested in maintaining so-called “cold chain” systems around the world, and this technology is a potential disruption to that.

"When you take that vaccine from the refrigerator, you really don’t know what happened to that vial before you got there."

There will also be regulatory hurdles to get through, although Filipe expects the process to be relatively smooth. The sugars were chosen in part because they are already approved by Health Canada and the U.S. Food and Drug Administration, and the process uses existing vaccines with well-established safety and efficacy.

The existing vaccines, though, are extremely fragile. Many need to be stored in a very cold freezer, and can only be held at fridge temperature (2 to 8 C) for a few days, during which time the countdown is on to get the medicine to the end user.

Any screw-ups or delays along the way will break the cold chain, rendering the medicine useless and vulnerable people unprotected, especially in rural, remote, and conflict-affected areas.

A simplified process, where a film could be dropped into a vial of saline, shaken for five seconds, and then injected, could help save lives and money, Filipe said.

Testing it with the vaccine against measles, which is back with a vengeance worldwide, is an especially urgent priority. Among the many outbreaks ongoing, the worst are in Madagascar, where 84,765 people were infected between October 2018 and March 2019, according to the WHO, as well as Ukraine (56,094), and India (19,544), which Filipe has visited many times.

“The power goes out very frequently. When you take that vaccine from the refrigerator, you really don’t know what happened to that vial before you got there,” he said.

“You can be using the cold chain, but also use this additional level of safety.”